Conventionally, transparent cosmetic compositions have been made using a soap/alcohol formulation. Such compositions have been formed as gelled sticks which act as vehicles for delivery of active ingredients.
U.S. Pat. No. 4,268,498 (Revlon) describes clear cosmetic sticks comprising a soap/alcohol gel base. It mentions two problems associated with previous soap/alcohol formulations: that the sticks are initially clear but become hazy with time, and that evaporation of the alcohol causes shrinkage of the stick. It proposes the use of polyoxyethylene-glucose fatty acid esters and of ethers of long-chain alcohols to replace short-chain monohydric alcohols. However, desirable cosmetic features such as cooling effect are thereby lost.
In EP 107 330 (Procter & Gamble), there is disclosed a transparent soap gel stick composition which contains hydro-alcoholic soluble emollient. The composition contains less than 12.5% of a short chain monohydric alcohol, e.g. ethanol. However, there is not mention of the inclusion of a clarity-inducing component.
Transparent sticks can be prepared and manufactured by ensuring complete neutralisation of the fatty acids, but this requires an increase in the pH of the composition to unacceptably high levels, approximately pH 10.
Further neutralisation to pH 7 means that free fatty acid will be present which may form acid soap crystals providing nucleation sites leading to the growth of large soap crystals. This growth of large crystals destroys the transparency of the composition either immediately or on gradual cooling.
It has surprisingly been found that when certain compounds are included in the cosmetic composition, the growth of soap crystals in the composition is inhibited, and transparency is achieved even at high levels of monohydric alcohol. Furthermore, such compositions can, if desired, be formulated entirely from natural plant-derived materials, that is, materials obtained from microbial culture and/or from higher plants.